What does the future hold for New York’s moose?

December 11, 2013

Moose once inhabited northern New York in great numbers, but as a result of habitat destruction and relentless hunting, they were eliminated during the 19th century. It is widely accepted that the last native Adirondack moose was an 800-pound cow shot near Raquette Lake in 1861. Two attempts at re-establishing a viable population by releasing them in Hamilton County, one in 1894 to 1895 and the other in 1902 to 1903, failed.

It wasn't until the 1980s that moose returned to northern New York, probably due at least in part to reduced logging and an increase in the application of sustainable forest management practices by forest landowners both within the Adirondack Park and outside of the Blue Line, which has resulted in the recovery of extensive and superior habitat at a time when range is diminishing due to continued encroachment by humans in nearby areas, especially in Canada.

Records of their breeding began in 1990, and since 2007, the state Department of Environmental Conservation has been conducting early winter aerial surveys over known moose habitat in the northeastern Adirondacks to better assess moose populations. DEC has also been asking hunters, trappers and the public at large to report locations and numbers when moose are sighted. They rely heavily on these sighting reports when making moose population assessments.

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(Enterprise file photo)

The moose population in New York is now estimated at upwards of 800 and growing. And since calves generally remain with their mothers for about a year, until the mother calves again and individuals other than adult males sometimes herd together in winter, reports by lucky observers of two, three or more animals moving together continue to increase.

Unfortunately, moose populations have been declining at very disturbing rates across much of their southernmost North American range and their fate in many of these areas now seems to be very much in question. While the specific reasons for the decline are several, and apparently vary from location to location, scientists agree that warmer, shorter winters are at least part of the underlying cause. First off, moose amass a considerable quantity of body fat in the months leading up to winter, and when temperatures rise above 23 degrees Fahrenheit, they must expend substantial amounts of energy just trying to stay cool, which can lead to exhaustion and ultimately death.

But changing climate has also impacted moose populations in ways that are considerably less obvious. In western Canada, in the Cariboo Mountains of British Columbia, warmer winter weather has resulted in an epidemic of pine bark beetles that have literally wiped out vast expanses of moose habitat, leaving moose abnormally vulnerable to predators, animal and human. Populations have fallen by as much as 70 percent in some areas.

In Minnesota, home to two geographically separate moose populations, one herd, the northwestern herd, has dwindled from a population of about 4,000 to fewer than 50, in just 20 years. Based on aerial surveys, Minnesota's northeastern population has declined, too; by nearly 70 percent, from approximately 9,000 in 2006 to an estimated 4,230 just one year ago and fewer than 2,800 today.

While scientists in Minnesota believe that the increase in mortality is, to some extent, from heat stress resulting in predation, they are also looking at two parasites, brain worms and liver flukes, as major contributing factors. Both are carried by, but not generally considered harmful to, white-tail deer. Both, however, can be deadly to moose. Researchers there have also begun looking at stress-related mortality due to increasing numbers of winter ticks (which should not be confused with dog ticks or deer ticks, whose numbers are also on the rise). Because moose populations have declined so quickly, Minnesota no longer has a moose hunting season.

Closer to home in New Hampshire, where milder, shorter winters and less snow have markedly increased the survival rate of winter ticks, moose are being profoundly affected. Their number has plummeted from about 7,500 in 2008 to roughly 4,500 today. Winter ticks have taken an even greater toll on moose in Vermont where, since 2008, the moose population has been cut in half, from roughly 5,000 to an estimated 2,500.

By contrast, in Maine, colder winters and ample snowfall still hold tick populations in check, at least in northern regions of the state. And even though moose living in southern portions of the state are being impacted by increasing numbers of winter ticks, the state's overall moose population remains stable at more than 75,000.

The success of winter tick populations is closely tied to early- and late-season cold and snowpack. In the fall, they remain on low-lying vegetation until they are able to climb aboard a passing host. They feed on that one animal throughout the entire winter, until the spring, when they drop from the host to lay their eggs on the ground. Cold weather and sufficient snowpack early in the year will kill many of the ticks before they are able to find a host. Ample snowpack late in the year prevents them from laying as many eggs.

When their populations are high, tens of thousands of winter ticks can parasitize a single moose. In fact, wildlife biologists have records of individual animals carrying tick loads of as many as 150,000 insects. Large infestations can result in reduced fertility in moose cows and reduced growth rates in moose calves. What's more, anemia and loss of weight and hair (actually hair breaking off at the skin from constant scratching) can be so severe that observers have reported seeing hairless moose. These animals have come to be known as "ghost moose." Once a moose loses its winter coat, it will almost always, sooner or later, fall victim to hypothermia.

Studies being initiated in several states may be able to provide better clarity about the risks currently facing moose populations, but stopping the declines - well, that's another story. No one knows what the future holds for moose here or elsewhere, but scientists are very concerned.

The good news for now is this. According to DEC information, winter ticks have yet to be documented in New York. In fact, it appears that the cause of most known moose mortalities here, in northern New York, is collision with motor vehicles.